Kent Johnson wrote on 19.11.2005: >Danny Yoo wrote: >>Here's a small example that shows how classes can be treated just >>like any other value in Python: >> >> ######################################### >> def makeYa(superclass): >> class Ya(superclass): >> def sayHi(self): >> superclass.sayHi(self) >> print "ya" >> return Ya >> >> class ValleyPerson: >> def sayHi(self): >> print "like, so, oh my gosh, hi?" >> >> FrankensteinClass = makeYa(ValleyPerson) >> instance = FrankensteinClass() >> instance.sayHi() >> ######################################### > >Yeah, that'll work too :-) Or even > >def makeAB(moduleContainingSuperClass): > class A(moduleContainingSuperClass.A): > pass > class B(moduleContainingSuperClass.B) > pass > return A, B > >A, B = makeAB(siteA) > >>So there's no need to do trickery with conditional imports; Python >>treats classes as first-class objects that can be passed around. > >Trickery? ;) It's just using modules as first-class objects that are >bound to names same as anything else. Which solution is better >depends on whether you want to choose at the module level or with >finer control.
Hm, sounds like there's more than one way to do it. ;-) Thanks a lot for your examples. I hate to confess that I incorrectly described my requirements. It turns out that I am better off with a (variant of the) state design pattern. But I am stuck there, too. The situation is this: For every object, two string attributes are determined during initialization (one being read from a database, the other inherited as a superclass attribute). The first contains the site name, the second the object type. I'd like to set the template attribute to the proper class: import Templates self.site_name = 'SiteA' self.template_type = 'Page' self.template = ??? self.template should refer to Templates.SiteA.Page in this case (where SiteA is a module of package Templates, and Page is a class within that module). Danny already said that classes can be treated just like any other object - but how do I get from a string to a class or module name? Thanks for all your help, and sorry for my ignorance, Jan -- Any sufficiently advanced technology is indistinguishable from a Perl script. - Programming Perl _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
